In generally, a secondary battery capable of repeating charge/discharge, unlike a primary battery, has been developed according to the development of high-tech products, such as a digital camera, a cellular phone, a notebook computer, a hybrid vehicle. The secondary battery includes a Ni—Cd battery, a Ni-metal hybrid battery, a Ni—H battery, a lithium rechargeable battery and the like. The lithium rechargeable battery having an operating voltage of 3.6 V or more is used as a power source for various portable electronic instruments, or a plurality of lithium rechargeable batteries are connected in series and used in a high power hybrid vehicle. Since the lithium rechargeable battery has the operating voltage that is three times higher than that of the Ni—Cd battery or the Ni-metal hybrid battery and also has excellent characteristic of energy density per unit weight, its use is sharply increased.
The lithium rechargeable battery can be manufactured in various types, e.g., a cylinder type and a prismatic type which are mainly used in a lithium-ion battery. Recently, a lithium polymer battery is manufacture in a pouched type having flexibility, and thus it can be freely formed into various shapes. Further, since the lithium polymer battery is light and has excellent stability, it is advantageous in forming much slimmer and lighter portable electronic instruments.
FIG. 1 is a view showing a structure of a conventional pouched type lithium rechargeable battery. The conventional pouched type lithium rechargeable battery includes a battery part 51, and a case 10 that provides a space 11 for receiving the battery part 51.
In the battery part 51, an anode plate, a separator and a cathode plate are arranged in turn and then wound in one direction, or a plurality of anode plates, separators and cathode plates are stacked. Each electrode plate of the battery part 51 is electrically connected with an anode tap 52a and a cathode tap 52b. 
One ends of the anode tap 52a and the cathode tap 52b are protruded through a closed surface 12 of the case 10 to the outside. The protruded ends of the anode tap 52a and the cathode tap 52b are connected with a terminal of a protection circuit board.
An isolating tape is wound on the anode tap 52a and the cathode tap 52b to prevent electrical short between the case 10 and the anode tap 52a and the cathode tap 52b at a portion contacted with the closed surface 12.
The case 10 has a pouched type structure including a middle layer formed of a metal foil and inside and outside layers formed of an insulation film, unlike a can type structure such as a cylinder type or a prismatic type that is thickly formed of a metallic material. The pouched type case has excellent formability and flexibility. The case 10 is formed with the space 11 for receiving the battery part 51, as described above, and the closed surface 12 is thermally bonded along an edge of the space 11.
FIG. 2 is a cross-sectional view taken along a line A-A of FIG. 1. The case 10 is formed of a complex film including a middle layer formed of a metal foil, e.g., an aluminum foil and inside and outside layers formed an insulation film that is attached to inner and outer surfaces of the middle layer so as to protect the middle layer.
The battery part 51 in which an anode plate 51a, a separator 51c and a cathode plate 51b are arranged in turn is received in the space 11 of the case 10, and the anode tap 52a and the cathode tap 52b are extended from the anode plate 51a and the cathode plate 51b. Ends of the extended electrode taps 52a and 52b are protruded through the closed surface 12 of the case to the outside, and outer surfaces of the electrode taps 52a and 52b that are contacted with the closed surface 12 are wound with an insulating tape 13.
In a pouched type lithium rechargeable battery 50, as described above, the battery part 51 is finished by electrically connecting the electrode taps 52a and 52b and the anode plate 51a and the cathode plate 51b and then winding them in one direction in the status that the anode plate 51a, the separator 51c and the cathode plate 51b are arranged in turn.
The finished battery part 51 is installed in the space 11 of the case 10 through a drawing process. One end of each electrode tap 52a, 52b is exposed to the outside of the case 10 upon the installing. In this situation, the pouched type lithium rechargeable battery 50 is finished by a thermal bonding process that applies predetermined heat and pressure to the closed 11 of the case 10. In order to stabilize the battery structure, the finished pouched type lithium rechargeable battery 50 is treated by a formation process including charging, aging, discharging and the like, thereby determining whether the battery is normal or abnormal.
Along this line, Korean Patent Publication No. 2005-000594 discloses a method casing a pouched type lithium rechargeable battery. In this pouched type lithium rechargeable battery, as the same anode potential is applied to an anode tap and a metal layer of a case, when a cathode tap is contacted with a metal layer of the case due to breakage of an inside layer of the case, electrical short is induced so as to easily detect voltage difference of an open circuit.
Meanwhile, in case that a high-power lithium battery is necessary for the hybrid vehicle, a few tens to a few hundreds pouches are stacked and then connected to each other in series so as to obtain a high voltage.
Since the pouched type lithium polymer battery is formed of a flexible aluminum pouch which can be easily bent, it has to be protected by a hard case to be used for a long time. However, in the conventional battery, the anode tap and the cathode tap of each pouch are connected by a printed circuit board (PCB) having a circuit pattern in order to connect the plurality of pouches in series, and then the connected pouches are received in the case.
However, in the conventional method of forming a high power lithium battery by stacking the plurality of lithium polymer pouches, since the flexible lithium polymer pouch cannot be protected completely and securely and the method of connecting the stacked pouches using the PCB is also imperfect, it cannot resist an environment change.
Therefore, there is required a method of securely and stably stacking the pouch units forming the high power lithium battery as a power source and then connecting them in series or parallel.